Field of the Invention
The present disclosure relates to a sheet feeding apparatus.
Description of the Related Art
A certain conventional image forming apparatus such as a printer, a copier, and a facsimile is configured to feed a sheet stacked in a sheet feed cassette by a pickup roller provided in a sheet feeding apparatus and to convey the sheet to an image forming portion. The sheet feeding apparatus includes a separating portion configured to separate the sheet one by one even if two or more sheets are delivered by the pickup roller.
As one example of the separating portion, there is a retard separation type separating portion including a feed roller rotating in a same direction with the pickup roller and a retard roller that comes into pressure contact with the feed roller with a pressure contact force (referred to as a ‘nip pressure’ hereinafter) having a predetermined magnitude.
A driving force is applied to the retard roller in a direction opposite from the normal direction (referred to as a ‘reverse rotation direction’ hereinafter) in which the sheet is conveyed and which is the same direction with that of the feed roller through an intermediary of a torque limiter with a certain torque (referred to as ‘rotation torque’ hereinafter). That is, the retard roller is capable of rotating both in the normal and reverse rotation directions.
This retard separation type separating portion is configured to prevent sheets from being fed doubly by reversely rotating the retard roller when two or more sheets enter a nip portion (referred to as a ‘separation nip portion’ hereinafter) between the retard roller and the feed roller. In a case where one sheet enters or no sheet enters the separation nip portion, the retard roller normally rotates together with the feed roller.
Concerning the retard separation type separating portion, a configuration of attaching each roller at an end portion on a free end side of a driving shaft supported in a cantilever condition is adopted more often lately to improve replicability of the retard and the feed rollers as disclosed in U.S. Pat. No. 8,511,674. It is possible to readily carry out a roller replacing work by removing each roller from the free end of the driving shaft by releasing a lock mechanism provided at an end portion of each roller.
However, a sheet feeding apparatus as described in U.S. Pat. No. 8,511,674 causes the following problems. That is, if the retard roller comes into pressure contact with the feed roller and the feed roller rotates in separating and feeding a sheet, the retard roller receives a load from the feed roller and the free end side of the driving shaft supporting the feed roller is displaced to a downstream side. Thereby, the retard roller is misaligned from the feed roller, possibly causing uneven wear of the retard roller and the feed roller. If the retard roller or the feed roller unevenly wears, there may be a problem that durability of the retard roller or the feed roller drops, thus also dropping sheet conveyance performance.